Frame Relay Questions
Normal (Ethernet) ARP Request knows the Layer 3 address (IP) and requests for Layer 2 address (MAC). On the other hand, Frame Relay Inverse ARP knows the Layer 2 address (DLCI) and requests for Layer 3 address (IP) so we called it “Inverse”. For detail explanation about Inverse ARP Request please read our Frame Relay tutorial – Part 2.
When saying “Frame Relay point-to-point” network, it means “Frame Relay subinterfaces” run “point-to-point”. Notice that Frame Relay subinterfaces can run in two modes:
+ Point-to-Point: When a Frame Relay point-to-point subinterface is configured, the subinterface emulates a point-to-point network and OSPF treats it as a point-to-point network type
+ Multipoint: When a Frame Relay multipoint subinterface is configured, OSPF treats this subinterface as an NBMA network type.
And there are 4 network types which can be configured with OSPF. The hello & dead intervals of these types are listed below:
|Network Type||Hello Interval (secs)||Dead Interval (secs)|
Therefore the default OSPF hello interval on a Frame Relay point-to-point network is 10 seconds.
Traffic shaping should be used when:
+ Hub site (headquarter) has much faster speed link than the spokes (remote sites). In this case we need to rate-limit the hub site so that it does not exceed the remote side access rate
+ Hub site has the same speed link as the spokes. For example both the headquarter and the spokes use T1 links. In this case, we need to rate-limit the remote sites so as to not overrun the hub.
An example of configuring traffic shaping is shown below:
interface Serial0/1.10 point-to-point
ip address 10.10.10.10 255.255.255.0
frame-relay interface-dlci 10 class my_traffic_shaping
map-class frame-relay my_traffic_shaping
frame-relay adaptive-shaping becn //Configure the router to respond to frame relay frames that have the BECN bit set
frame-relay cir 128000 //Specify the committed information rate (CIR) for a Frame Relay virtual circuit
frame-relay bc 8000 //Specify the committed burst size (Bc) for a Frame Relay virtual circuit.
frame-relay be 8000 // Specify the excess burst size (Be) for a Frame Relay virtual circuit.
frame-relay mincir 64000 // Specify minimum acceptable CIR for a Frame Relay virtual circuit.